The present invention relates to coatings formulations with relatively high opaque polymer pigment volume concentration (PVC) in combination with fully or partially polymer encapsulated TiO2 particles and relatively low levels of extender.
In the paint industry, formulators rely on TiO2 as a pigment to achieve excellent hiding characteristics; nevertheless, the high cost of TiO2 has motivated formulators to seek ways of improving its efficiency. One approach is to use a lower concentration of TiO2 in conjunction with opaque polymer, which is known to provide equivalent hiding but at a lower cost. Unfortunately, as disclosed in U.S. Pat. No. 4,474,910, unless opaque polymer is used in small amounts, burnish resistance of the final paint formulation suffers.
The addition of a coarse extender such as silica or calcium carbonate provides a way of increasing burnish resistance in paints containing opaque polymer at a pigment volume concentration (PVC) that would otherwise produce unacceptable burnish resistance. However, the presence of an extender flattens the appearance of the coated paint, thereby limiting the formulator to making either flat paints with relatively high levels of opaque polymer, or a gloss or semi-gloss paint with relatively low levels (<15 PVC) of opaque polymer. It is therefore desirable to find a way to increase the amount of opaque polymer that can be used in a gloss or semi-gloss paint formulation while maintaining acceptable burnish resistance.